Controlling the grain formation process with oleylamine and 4-dimethylaminopyridine additives for efficient and stable MAPbI3 solar cells

Abstract

MAPbI3-based perovskite solar cells (PSC) prepared on one-dimensional structured electron transport layers (ETL) have been widely investigated due to excellent photovoltaic properties. However, they have displayed lower stability and power conversion efficiencies compared to other perovskite solar cells such as FAPbI3 and mixed halide perovskites. To improve the quality of perovskite film, we treat MAPbI3 perovskite layer with oleylamine (OAm) and 4-dimethylaminopyridine (DMAP) during preparation. Modified MAPbI3 layers are prepared by spin coating OAm-added precursor solution on ETLs and the DMAP solution is dripped on the rotating substrate during spin coating process. The OAm additive not only enhances significantly the perovskite crystallinity but also reduces the number of pin-holes inside perovskite thin films. The drip starting time of DMAP solution strongly affects the nanostructures of perovskite layer and the PSC performances. The best efficiency of PSC in this study is 20.49 % and is the highest cell performance compared to other MAPbI3-based PSCs using TiO2 nanorod thin films as ETLs in literature. The remarkable enhancement of PSC performance is assigned to the synergetic effects of both DMAP and OAm at the grain boundaries of MAPbI3 layer. Furthermore, the use of OAm and DMAP leads to significant enhancement of device's stability under ambient conditions.